The present invention pertains to the signal processing art and, more particularly, to detector circuitry for producing an indication of the relative level of an AC signal.
Signal strength detectors are well known, especially in the radio communication art. Here, there are numerous applications wherein it is desirable to produce a DC signal whose magnitude is representative of the level of an AC signal. Heretofore, there have been several systems which processed an AC signal via a cascade arrangement of amplifiers, each feeding an individual detector, for producing an output signal having a DC magnitude representative of the log of the input AC signal.
Recently, the development of a sectored antenna receiving system has required the use of a wide range signal detector which is capable of producing an output DC signal whose magnitude is linearly related to the quieting level of an FM receiver. This sectored antenna receiving system is more fully described in a copending U.S. patent application entitled "Sectored Antenna Receiving System" invented by James Stimple and Timothy Craig, Ser. No. 792,963, filed May 2, 1977, and an additional U.S. patent application entitled "Sectored Antenna Receiving System", invented by James Stimple, Timothy Craig and Paul Erickson, Ser. No. 792,961, filed May 2, 1977, both of said applications being assigned to the same assignee as the instant application. There, a scanning system constantly couples each one of a plurality of antenna sectors to receiver circuitry. Scan control logic monitors the signals received by each sector to operate in additional scanning modes. Proper operation of these systems requires signal detector circuitry which is capable of monitoring the intermediate frequency level of signals received from each sector and to then produce a DC signal having a representative magnitude. Thus, a signal detector for use in this application must have a response characteristic which tracks that of the inherent quieting response of the FM receiver. None of the prior art signal detectors, most of which have a logarithmic response, would be suitable for providing the precise tracking required in the aforementioned sectored antenna receiving systems.
A further requirement imposed on a signal detector for use in the above application is that it must be capable of handling signal levels over a broad dynamic range.